Process of electrical reduction.



C. H. FULTON. PROCESS OF ELECTHICAL REDUCTION.

APPLICATION min JULY 25. 1911.

1,267,347. Patented May 21,1918

JET J un'irun swims PATENT OFFICE.

CHARLES H. FULTON, OF ST. LOUIS, MISSOURI,-ASSIGNOR TO METALLURGICAL LABORA- TORIES, INCORPORATED, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

PROCESS OF ELECTRICAL REDUCTION.

Specification of Letters Patent.

Patented May 21. 1918.

Application filed July 25, 1917. Serial No. 182,711.

To all whom it may concern:

Be it known that I, CHARLES H. FULTON, a citizen of the United States, residing at St. Louis, Missouri, have invented a certain new and useful Improvement in Processes of Electrical Reduction, of which the followin is a full, clear, and exact description, suc as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to a process for the reduction of metallic oxids, sulfates or other compounds.

The process now generally used for reducing substances of the character above referred to consists in mixing a reducing agent with the substance to be reduced so as to form a loose granular mixture and then feeding said mixture through a long cylindrical kiln that is heated by oil or gas. Such a process is slow and imperfect. For example, in the reduction of barium sulfate to barium sulfid for use in the manufacture of lithophone, the yield of water soluble barium sulfid rarely exceeds 60% in practice.

The main object of my invention is to provide a process for the reduction of metallic oxids, sulfates or other compounds which insures a greater ield of the resultant product than could be obtained by the process heretofore in general use.

Another object is to provide a rapid process for the purpose described that can be accurately controlled.

Another object is to provide a practicable and inex ensive process for producing barium sul d.

And still another object is to provide a briquet of novel composition for use in re duction furnaces.

To this end I have devised a process, which, briefly described, consists in mixin the substance to be reduced with a materi that is a conductor of electricity, and some instances, adding a reducing agent or reagent to the mixture, forming said mixture into objects that will retain substantially their original form and volume when heated to a tern erature suflicient to bring about'the desire reduction, arranging one or more of said objects between the electrodes of an electrically-operated reduction furnace so ma form a fixed resistor, then into a coherent mass.

passing a current of electricity through said ob ect or objects so as to generate sufficient heat within said objects to bring about the desired reduction, and thereafter treatmg said object or objects so as to recover or remove from said objects the product of the reduction operation.

It is immaterial, so far as my broad idea is concerned, how said. objects are formed, but I prefer to form them by combining the substance to be reduced, in a finely-divided form, with material which is a conductor of electricity and with a bindin material mixed in certain proportions, an thereafter forming said mixture into solid objects or briquets under high pressure. In some .instances it is necessary to incorporate a reducing agent or reagent in the mixture during the operation of forming the briquets. The electrical conducting material that I prefer to use in the composition of the briquets is finely-divided coke, as such material is porous; it is a good electrical conductor and it also serves as a reducing agent in the reduction of certain substances. Furthermore, finely -divided coke presents a stable and unchangeable material about which the body of the briquet is formed, thus insuring the continued *stability of the briquet during and after the reduction operation. Various binding substances or materials may be used, but I prefer to use a carbonaceous binding material, such, for example, as cause after the volatile matter is distilled from it there is left a solid coke residue which firmly binds the particles of coke and the particles of the substance being reduced The proportions of the substance to be reduced and the other substances or materials used in the com osition of the bri uets will vary with di erent metallic oxi s, sulfates and other comounds, but the essential thing in respect to the substance to be reduced and the coke is that they shall be in a finely-divided state and of such proportions that there will be.

cient mass of porous material to maintain the ap roximately original form and volume of the briquets. The essential thing about the quantity of binder is that it shall be suflicient to unite all ingredients into a coherent mass by its adhesive action when the briquets are first formed and also hold the ingredients together when the briquets are thereafter heated to bring about the desired reduction. It is preferable to heat the mixture or add the binder in a molten state to the other ingredients during the operation of formin the briquets, so as to cause the particles 0 the various ingredients to become thoroughly coated with the binder. 1o .The shape of the briquets is immaterial, but in ractioe I prefer to form the briquets into sp erical, cylindrical or other preferred form in molds wherein they are subJected to a pressure of between 500 lbs. and 1000 lbs. to the square inch, so as to solidify the mixture and form it into a compact mass that will not swell and crack during the subsequent reduction operation. When a carbonaceous binding material is used it is desirable to preheat the briquets after they have been removed from the molds or just prior to the reduction operation, so as to drive off the volatile matter in the binding material and convert said binding material into a substance that is a good electrical conduetor, namely, coke. To secure the most advantageous results the above described preheating and drying of the briquets must be done under strict y non-oxidizing conditions, for if oxygen is permitted to reach the briquets during this operation, the coke WillOXldlZG on the surface of the briquets and cause the outside of the briquets to assume a loose and friable condition, with re- 85, sulting disintegration of the surface of the briquets.

A bri uet produced in the manner above describe consists practically of a coke matrix or cellular structure whose cells are filled with the substance that is to be re duced. This matrix or cellular structure is made u of the coke with which the substance to e reduced is first mixed and the coke left by the distillation of the carbonaceous binder, audit is of such a character that it will retain both its original form and volume during the reduction operation and will serve as a proper resistor conductor between the electrodes of .an electric reduction furnace. After the briquets have been formed in the manner above described one or more of the bri nets are arranged between the electrodes 0 an electric reduction furnace, so as to form a fixed resistor.

A current .of electricity is then passed through said briquets so as to heat them sufliciently to bring about the desired reduction. Thereafter, the briquets are treated in any suitable manner, so as to recover the 60 product ofthe reduction operation.

Fi ure'l of the drawings is a vertical sectiona view of an apparatus that can be used in practisin' my process; and

Fig. 2 is a top p an view, partly in horizon 66 twl section of the apparatus shown in Fig. 1.

The apparatus shown in the drawings is intended to be used in the production of barium sulfid, but 'it can be used equall well for the production of a calcium sulfir sodium sulfid or other sulfide. Said apparatus comprises a vertically-disposed, hollow member A that forms the chamber of an electric reduction furnace, a base B on which the member A is removably mounted and an incline D that slopes downwardly from the base B to a tank E filled with water that is used for treating the briquets after they have been heated in the furnace A. The chamber of the furnace is provided at its upper end with an opening 1 that is normally closed by a cover 1, and one or more ports 2 are formed in the walls of the furnace so as to permit the gases to escape from the furnace chamber during the reduction operation.

In using my process for the production of barium sulfid I mix approximately 100 parts of finely crushed barytes (which is barium sulfate) with 70 to 85 parts of finely crushed coke and approximately 20 parts of pitch and form said mixture into large briquets from 9 to 12 inches in diameter and from 3 to 6 feet in length in the manner previously described. After the briquets,

have been preheated and dried a number of them are'arranged on the base of the reduction furnace so as to form a plurality of vertical columns C whose lower ends rest on the electrodes 3 of e furnace and whose upper ends are conne ted together by connecters 4, as shown in Fig. 1. After the briquets have been set up and connected together inthe manner described the member A is arranged in operative position on the base B over the briquet columns by means of a crane that comprises a truck 6 that travels on overhead rails 5 and a truck 7 that travels on rails 5 carried by the truck 6 and arranged at right angles to the rails 5, themember A bein suspended from the truck 7 by means of c ains=8. Thereafter, the current is turned on so as to heat the briquets. At a temperature between 800 and 1000 C. the barium sulfate is comletely reduced to barium sulfid. The hot riquets are then discharged into the water in the tank D and are leached practically free fFom the barium sulfid. It is, of course, immaterial, so far as my invention is concerned,,how the electric current is supplied to the briquet columns, so long as the electrical resistance is such as to cause a sufficient heat development within the charge itself to bring about the desired reduction. By .varymg the amount of current sent through the bri uet columns C thespeed of reduction may e kept under perfect control. The current is preferably supplied to the furnace through a transformer so designed as to supply current of different volt-I ages. If the current is too great or too small at any given voltage, the voltage of the transformer may be decreased or increased until the proper fiow of current is obtained. In the apparatus herein shown the base B is provided with two sets of electrodes 3 so as to permit a charge to be set up on one set of electrodes while a charge product of the reduction op on the, other set of electrodes is being reduced. At the completion of the reduction operation the member A that constitutes the chamber of the furnace is raised slightly by means of a crane and then moved forwardly toward the tank E, so as to cause said member A to drag the briquets forwardly toward the incline D down which they travel to the water in the tank E. The member A is then elevated and moved laterally toward the char e that has been previously set up on the 05161 set of electrodes and is lowered into operative position over said charge. If desired, the heat stored in the walls of the member A during the previous reduction operation can be used to preheat and bake the second charge of briquets that is set up on the base B, thus overcoming the necessity of preheating and dr ing the briquets by a separate 0 eration. y process has the advantage 0 giving a much greater yield of barium sulfid than could be obtained by the process heretofore generally used for producing barium sulfid, and it is more rapid than the rior process. The greater yield obtained y my process is due to the very intimate contact of the substance to be reduced With the reducing agent, and the accurate temperature control that is made possible by the use of an electric current to heat the charge. The exclusion of all oxygen from the chamber of the furnace gives a perfect reducing atmosphere during the reduction operation, which is not possible in the process at present used, aiding materially the high yield obtainable in my process. While I have herein specifically described my process as being used for the production of barium sulfid, I wish it to be understood that it is applicable to the reduction of various metal ox'ds, sulfates or other com ounds.

aving thus described my invention, what I claim, and desire to secure by Letters Patent, is:

1. A process of reduction, characterized by forming the substance to be reduced into an object that-is an electrical conductor, passing a current of electricity through said object so as to heat it sufiiciently to bring about the desired reduction, and thereafter treating said object so as to recover the oration. 2. A process of reduction, characterized by forming the substance to be reduced into an electrical conducting object that will maintain approximately its original form and volume when subjected to the temperature at which the reduction takes place, passing a current of electricity through said ob ect so as to heat it sufiiciently to bring about the desired reduction, and thereafter treating said object product of the reduction operation.

3. A process of reduction, characterized by forming the substance to be reduced into briquets that will retain approximately their original form and volume when subjected to the temperature at which the reduction takes place, interposing one or more of said briquets as a continuous resistor between the electrodes of an electric reduction furnace, passing a current of electricity through said bri net or briquets so as to heat them suflicient y to bring about the desired reduction, and thereafter treating said briquet or briquets so as to recover the product of the reduction operation.

4. A process of reduction, characterized by forming the substance to be reduced into' briquets that will retain approximately their original form and volume when subjected to the temperature at which the reduction takes place, arran 'ng a plurality of said briquets in a close chamber, passing a current of electricity throu h said briquets until they are heated su ciently to bring about the desired reduction, and thereafter treating said briquets so as to remove the substance that has been reduced.

5. A process of reduction, characterized by mixing the substance to be reduced in a finely divided form with a granular material that is a conductor of electricity, forming said mixture into objects that will retam approximately their original form and volume when sub ected to the temperature at which the re uction takes place, and thereafter arranging a number of said objects in a closed chamber, assing a current of electricity through said objects so as to heat them sufliciently to bring about the desired reduction, and thereafter treating said objects so as to efi'ect the recovery of the product of the reduction operation. 6. A process of reduction, characterized by formin bri uets from the substance to be reduce a inely-divided material that is a conductor of electricity and a binding material mixed in such proportions that the briquets will retain approximatel their original form and volume when su jected to the temperature at which the reduction takes place, and thereafter passing a current of electricity through a plurality of said briquets while they are confined in a closed chamber so as to heat said briquets suflicientl to bring aboutthe desired reduction, and Iihally, treating said briquets so as to recover the product of the reduction operation.

7. A process of reduction, characterized so as to recover the l by forming a by formin bri acts from the substance to be reduc fine ydivided coke and a bind- 8. A rocess of reduction, characterized by formln briquets from the substance to be reduce in finely-divided form, finelydivided co e and a carbonaceous binding material mixed in such proportions that the briquets will retain approximately their original form and volume when subjected to the temperature at which the reduction takes place, thereafter heating said briquets suificiently to bring about the desired reduction by passing a current of electricity through one or more of said briquets while they are arranged in a closed chamber, and finally, treatin said briquets so as to recover the pro not of the reduction operation.

9. A rocess of reduction, characterized by formln bri uets from the substance to be reduce in ely-divided form, finelydivided colre and a carbonaceous binding material mixed in such proportions that the briquets will retain approximately their original form and volume when subjected to the temperature at which the reduction takes place, heatin the briquets so as to drive off the volati e matter in the binder, thereafter heating said briquets' sufficiently to bring about the desired reduction by passing a current of electricity through one or more of said briquets while they are arranged in a closed chamber, and finally, treating said briguets so as to recover the product of the re uction operation.

10. A process of reduction, characterized stance to be reduced, in finely-divided form, a finely-divided material that is a conductor of electricity anda' binding material, forming said mixture into briquets in molds wherein they are subjected to great pressure and'thereafter arranging one or more of said briquets between the electrodes of an electric reduction furnace so as to form a fixed resistor, passin a current of electricity through said br quets so as to beat them sufiicientl to bring about the desired reduction, and l mally, treatin said briquets so as to recover the product 0 the reduction operation.

11. A process by forming a mixture of reduction, characterized from the substance to mixture composed of the subbe reduced, a suitable rea ent or reducing agent and a material whic is a conductor of electricity, forming said mixture into indestructible briquets, of said -briquets in the path of an electric current so as to form a resistor, the heat generated by said current serving to bring about the desired reduction, and finally, treating said bri uetS so as to recover the product of there uction operation.

12. A process for producing barium sul fid, characterized by mixing crushed barium sulfate with a material that is a conductor of electricit and also a reducing agent, forming sai mixture into briquets that will retain approximately their original form and volume when subjected to a temperature high enough to bring about the desired re duction, passing a current of electricity through one or more of said briquets while they are confined in the chamber of an electric reduction furnace in engagement with the electrodes of said furnace, and subsequently treating the briquets with water after the reduction operation so as to leach he barium sulfid of the'barium for producing barium sul arranging one or more Y said briquets while they are confined in the chamber of an electric reduction furnace so as to heat said briquets sufiiciently to bring about the desired reduction, and thereafter immersing the briquets in water so as to leach them practically free from the barium sulfid produced by the reduction of the barium sulfate.

14. A process for producing barium sulfid, characterized by mixingbapproximately 100 parts of finely crushed arytes with 70 to 85 parts of finely crushed coke and approximately 20 parts of a carbonaceous binding material, forming said mixture into briquets that will retain approximately their original form and volume when subjected to a temperature high enough to reduce the barytes to barium sulfid, heating a plurality of said briquets bypassing a current of electricity through them while they are arranged in the chamber of an electri reduction furnace so as to form a fixed resistor between the electrodes of the furnace, and immersing the briquets in water after the reduction operation so as to leach them finely-divided coke and a binding material mixed in such proportions that said object w ll retain ap lilroximately its ori 1 form ind volume w on it is subjected to a tom- 5 pemture high'eno h to reduce the barium Lima.

sulfate tocbarium 16. An article use-in electrical-reduc tion furnaces, consisting of a molded object com osed of approximately 100 parts of fine y-divided barytes, 70 to 85 finely crush ed coke, and cgglroximatel 20 parts of a carbonaceous bin g mater-i CHARLES H. FULTON.

parts of 10 

